A light emitting diode (LED) has rapidly spread recently. With regard to a light emitting apparatus, such as the light emitting diode (LED) that has widely spread for use in a large display such as a TV and a PC, an information terminal for a touch panel, a cell phone and a smartphone, and lighting, a trend is to achieve high brightness. In such a current situation, high performance is also required for a sealing material used for the devices.
A method has been tried so far for performing resin sealing of an LED or the like by using as the sealing material a novolak-based epoxy resin, a cycloaliphatic epoxy resin or an acrylic resin, and hardening with acid anhydride or a polymerization initiator (see Patent literature Nos. 1 and 2, for example). However, the resins are deteriorated by heat or ultraviolet light from a light emitting device not to allow maintenance of high transparency, and thus have a disadvantage of causing colorization.
As a sealing material having a high transparency, a dimethyl silicone-based resin has been used (see Patent literature Nos. 3 and 4, for example). The resins are hardened by condensation between silanol groups, a hydrosilylation reaction between a carbon-to-carbon double bond and a SiH group using a platinum catalyst, a reactive functional group such as an epoxy group, or the like.
A resin mainly formed of dimethyl silicone can keep a higher transparency over a long period of time, even when exposed to heat or light, in comparison with a conventional epoxy resin, and therefore has been widely used as the sealing material for the LED or the like. However, the resin has problems such as a low adhesion to a base material, a lower refractive index of the resin in comparison with a value required as the sealing material, tackiness on a surface of a resin hardened material during LED manufacture, and easy scratching of a surface due to softness of a hardened film, and thus a further improvement has been required for the resin.
On the other hand, a siloxane-based resin synthesized by a sol-gel process has bee also studied as an LED sealing material (Patent literature Nos. 5 and 6). However, while the resin has a high surface hardness, the resin has a crack caused during hardening, distortion of a film by shrinkage during hardening, a low compatibility with other molecules, and therefore is not dissolved to be transparent without adding a large amount of diluent to cause a low viscosity, and thus the phosphor is easily settled out. Moreover, when a large amount of diluent formed of an organic component is added, a ratio of silicon in a resin composition decreases, and if exposed to heat or light for a long period of time, the resin has a problem such as a decrease in transparency.
Various types have been proposed for an optical semiconductor device package and a method for manufacturing the package. Above all, with regard to a resin composition containing a phosphor, a sheet for sealing an optical semiconductor, or the like, when the phosphor is uniformly dispersed into the resin composition, a fluctuation in chromaticity is minimized, and high brightness can be maintained (see Patent literature Nos. 7, 8 and 9, for example).
Thus, when a resin composition in which dispersibility of the phosphor is improved, or a processed sheet for sealing the semiconductor is used, an optical semiconductor package having a higher brightness can be produced. However, when the resin composition is provided as the sheet for sealing the semiconductor, a method for manufacturing the optical semiconductor package is limited.
Moreover, in a case where the phosphor is dispersed into the resin composition, the phosphor sinks during molding, and therefore is unevenly distributed. In a case where a plurality of color conversion materials are used, specific gravity of each material is different, and therefore the materials are not uniformly dispersed. Thus, the case has a problem of generation of color unevenness.
Furthermore, in a case where a device that emits light having a short wavelength, such as an ultraviolet light-emitting device, is used, the resin into which the phosphor is dispersed deteriorates by light from the device, and thus the case also has a problem of causing a change of color.
Accordingly, a liquid resin composition containing the phosphor is required to have an excellent dispersibility of the phosphor, and simultaneously in a case where the resin composition is processed and used as the color conversion material, to have a high heat resistance, resistance to thermal yellowing, transparency or surface hardness, and an excellent adhesion to a base material. However, a resin composition having a balance among various characteristics described above has not existed yet. Therefore, a resin composition having a good balance among the characteristics is desired.
On the other hand, a sealing process in manufacture of the optical semiconductor package has been applied by thermosetting so far in many cases, in which several hours are required in order to sufficiently harden the composition. In such a situation, a need is present for requiring a material that can increase a production rate.